Periodontal diseases are one of the most common bacterial infections of humans and impose a significant burden on the health care system. Recent developments in molecular based bacterial detection technologies have identified a number of previously unrecognized or under-appreciated organisms as associated with periodontal lesions. Here we propose to challenge an existing, well-defined model early-stage oral microbial consortium, consisting of Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus gordonii, with a newly recognized gram positive organism, Filifactor alocis, that has been strongly implicated as an important constituent of pathogenic biofilms associated with periodontal disease. As periodontal diseases are polymicrobial infections, in Aims 1 and 2 we shall characterize relative abundance changes in the transcriptomes and proteomes of F. alocis that occur as a result of close contact with the other organisms of differing pathogenic potential listed above. The transcriptome measurements will be time-coursed over the interval most likely to be informative of early stage adaptation to the community environment, from t=0 to t=12 hours, while proteomes will be sampled at 18 hours and other selected time points for non-targeted and targeted analyses. In Aim 3 mutants of F. alocis based on differential expression data will be generated and tested for community development by confocal microscopy and quantitative image analysis. As bacteria adapt to a community environment on a global scale, the systems based approaches of RNA-Seq and proteomics are essential for a full understanding of the differential expression patterns that characterize adaptation to polymicrobial communities. Interrogation of these datasets will provide novel insights into the pathoecology of F. alocis in the context of interactions with other organisms that are well-characterized. Overall, this project involves a comprehensive approach to address the pathoecology this newly recognized pathogen. Ultimately, the knowledge gained could be translated into novel diagnostic, therapeutic or preventive strategies for periodontal diseases.